Lamellar Architecture Affords Salt Cocrystals with Tunable Stoichiometry

Cocrystals typically display packing motifs distinct from their constituent components; this is a natural result of the new interactions being introduced disrupting those present in the pure components. Additionally, changes in stoichiometry within cocrystal systems are often accompanied by major changes in crystal packing, which can result in unpredictable changes in materials properties. Presented here is a suite of ammonium hexafluorophosphate pyrazinamide cocrystals that preserve the general packing motif, allowing a range of stoichiometries to be accessed without major changes to the noncovalent interactions or packing motif. This finding informs the design of salt cocrystals that are just beginning to affect the energetic materials field. These salt cocrystals break from the common motif of exploiting crown ether complexes and chart a path to compositions with a greater proportion of the oxidizing salt. The work is contextualized with a Cambridge Structural Database survey of existing salt cocrystals, and the properties of the cocrystals are examined for their dependence on stoichiometry.

Automated summary

Salt cocrystals typically exhibit distinct packing motifs and noncovalent interactions from their constituent components, with changes in stoichiometry potentially leading to unpredictable changes in materials properties. This study presents a series of salt cocrystals that maintain a general packing motif while allowing access to a range of stoichiometries, breaking away from the common motif of crown ether complexes and exploring compositions with higher proportions of oxidizing salt. The research provides insights for the design of salt cocrystals in the energetic materials field.